Metal, concrete, plastic and vitreous clay pipe is well known and extensively utilized for drainage, sewage and irrigation purposes. In all such applications, it is desirable to prevent water from leaking out of and into the pipes and also to prevent foreign objects, such as fines and debris, from entering the pipes at joints formed between adjacent pipe lengths.
Metal pipe is often corrugated or ribbed to provide improved structural strength. It is typically joined using band couplers which surround the joint and hold two adjacent pipe lengths together. Band couplers do not prevent water leakage from metal pipes since they do not provide a seal. Band couplers only serve to physically join the two pieces of metal pipe together.
Concrete, vitreous clay, plastic and similar pipes typically are joined by using various bell and spigot fittings formed upon the pipe ends. Each section or length of such pipe will commonly have a bell fitting formed at one end and a spigot fitting formed at the other end. These fittings are sized such that the spigot fitting can be received within the bell fitting. This mechanically joins two pipe lengths together, however it does not prevent water leakage from the pipe joint because the joint does not form a watertight seal. At best, the bell and spigot fittings merely serve to hold the ends of adjacent pipes in alignment as long as the spigot remains within the bell.
As is well known, when metal, concrete, plastic or vitreous clay pipe is used in subterranean formations, it is commonplace to back fill about the subterranean pipes and compact the back fill hard or tightly about the pipe. Due to this soil/pipe interaction, the pipe is supported in the formation to increase the structural integrity of the pipe within the formation. If substantial leakage of adjacent pipe lengths occurs at the joints between adjacent pipe lengths soil infiltration into the interior of the pipe may occur which through prolonged duration eliminates the soil/pipe interaction within the formation. As such, the pipe lengths are subject to moderate movement due to a failure of the back fill to support themselves which in some instances causes a subsidence of the overburden existing above the pipe lengths or in severe instances allows adjacent pipe sections to become disconnected from one another at their joints.
Further, the joints formed in the connection of metal, concrete, plastic and like pipe lengths are continuously subject to invasion by fine dirt, sand, and other foreign matter. Because of the poor seals formed by band couplers and bell/spigot joints, such foreign matter can work its way through the joint and eventually enter the pipe. Once inside the pipe, a buildup of foreign matter can restrict the flow of fluid therein, thus negating the effectiveness of the pipe. The debris from many such joints can accumulate at a single location, sometimes completely restricting water flow.
In recognition of these problems various means of sealing metal, plastic and concrete pipes and the like have been utilized in the prior art. Tapes, cast rubber gaskets, and flexible strips, as well as various chemical sealants have been used in an attempt to prevent water leakage from such pipes and also to prevent foreign matter from leaking into the pipes.
Numerous problems are encountered in the prior art attempts to seal such pipes. Pipes are typically subjected to a wide variety of environmental conditions, such as heat in the summer time, cold in the winter, settling of earth, and movement of the earth, as during earthquakes and construction.
The various sealing means of the prior art are subject to environmental degradation caused by the cyclic temperature changes and relative motion of the two pipe sections forming the joint. Cyclic temperature changes can cause many materials to become brittle and crack over extended periods of time, thus destroying the effectiveness of the sealing material. Relative motion of the pipe sections forming the joint can stretch and compress the sealing material, leaving the sealing material deformed or broken. This likewise destroys the effectiveness of the sealant. Further, prior art and rubber or elastomeric gaskets typically used in corrugated or other pipe sealing applications permanently set under compression within the pipe joints during installation and are incapable of expanding to re-seal the joint during later pipe joint movement.
Therefore, there exists a substantial need in the art to provide a sealing means which assures a watertight seal at the joints and is durable and flexible. The sealing means must be capable of withstanding cyclic temperature changes over extended periods of time and also be durable enough to endure reasonable, i.e. moderate, motion at the pipe joint without becoming permanently deformed or damaged. As such, although the prior art has recognized the need for sealing metal, concrete, plastic, clay pipe and the like from water leakage and the intrusion of foreign matter, the proposed solutions have to date proven generally ineffective in providing a satisfactory remedy.